It's easy to think you have the measure of 25-year-old Birmingham singer-songwriter Laura Mvula. The nomination for the Brits Critics' Choice award, the presence of former Rumer collaborator Steve Brown, comparisons to Amy Winehouse, Nina Simone and Billie Holliday, the forthcoming support slot on Paloma Faith's tour: it all seems to suggest yet another addition to the mountain of Radio 2-friendly retro-soul.

It's hard to react to that prospect with anything other than a weary groan, unless, of course, you're one of the hundreds of thousands of people who, nearly eight years after Amy Winehouse's Back to Black, keep buying albums made in its image with astonishing alacrity. It's like they're panic-buying the stuff in the erroneous belief there's going to be music rationing or something. Perhaps they think Radio 2-friendly retro-soul is going to be made illegal in an attempt to preserve the sanity of the rest of us. Whatever the reason, it still sells, so you can't blame Mvula's record label for trying to give the impression that's what's on offer here. Neither of the singles it's thus far picked are bad songs, but they seem to have been chosen in an attempt to shunt Mvula firmly into the middle of the road. She is a delicately lovely ballad, flecked not just with subtle orchestration but massed-harmony vocals somewhere between 60s sunshine pop ensemble the Free Design and the Swingle Singers, had the Swingle Singers got beatifically stoned before entering the studio. The perkier Green Garden (Behind the Scenes) sees Mvula's voice coated with a thin layer of distortion, as if on an old vinyl LP, and comes with a video featuring what the choreographer responsible describes a little vaguely as "ethnic dancing": the overall effect is to suggest that Mvula would once have been called nu-soul, cut from similar cloth to headwrap-era Erykah Badu or Angie Stone, albeit one who's written a musical tribute to the verdant pleasures of the parks in Birmingham's Kings Heath area.

The presence of harmonies that sound like a stoned Swingle Singers and Green Garden's unlikely subject matter might suggest there's something more intriguing about Mvula than the advance publicity implies. The rest of Sing to the Moon bears that out. Listening to it, you do wonder a little at the comparisons to soul singers past: Mvula's voice sounds no more like Billie Holliday than it does Billy Bragg, Billy Idol or indeed Billy Connolly; it's no more like Nina Simone than it is Nena who did 99 Red Balloons. You do occasionally get hints of influences, although not always the ones people have suggested. Sometimes, as on Make Me Lovely, the sound takes on the velvety lushness of the Carpenters(given his Carpentersesque work with Rumer, they to be something of an obsession of Brown's), while elsewhere you pick up on what appears to be an echo from Mvula's past as a gospel singer: Father Father certainly has a hymn-like quality, although that is disrupted by jarring, jazzy chords, as befits a song about her parents' marriage collapsing.

But for the most part, Mvula and Brown appear to have carved out a sonic space entirely of their own. The album's instrumentation is largely based around celeste, harp and double bass, the latter played pizzicato, which by modern pop standards is pretty leftfield. There's something thrilling about her use of harmonies, as on the opening Like the Morning Dew: massed, multi-tracked vocals suddenly crash into sparsely furnished songs. You could say something similar about Mvula's songwriting. On Is There Anybody Out There?, the chorus heads off at a weird melodic tangent to the rest of the song, while Make Me Lovely keeps fragmenting, breaking down into hushed interludes when you expect it to go hurtling towards a triumphant climax.

Indeed, it feels like it takes an age for Make Me Lovely to reach its conclusion, which brings us to Sing to the Moon's one big drawback. There comes a point, about four minutes into Can't Live Without the World, where you feel you've definitely got the idea of the song – the soft-pedalling orchestration, the heavy-lidded small-hours pace, the eerie, almost Broadcast-like hook. That moment is swiftly followed by another moment, where you realise you're barely two-thirds of the way through the thing. And comes then another moment, this one quite dispiriting, where it dawns on you that the song isn't going to do anything different in the remaining two minutes. This kind of thing keeps happening on Sing to the Moon. For want of a bit of editing, Mvula makes an abundance of interesting ideas feel like a paucity, dragging things out to fill space that doesn't need to be filled; if you knocked 10 minutes off its length, Sing to the Moon would still be the length of an album.

Still, that's a single complaint, and there are lots of things to recommend Sing to the Moon, not least that all its idiosyncracies of songwriting and arrangement and delivery feel meant: unlike some of the artists to whom she's been compared, you're never struck by the sensation Mvula is killing herself to appear kooky. But, then, the world into which she is being pitched doesn't really fit her. It thrives on cosy familiarity, on records that remind listeners of other records: Sing to the Moon feels more ambitious than that. Perhaps the best recommendation you can give Laura Mvula is that she patently isn't what people say she is.